"slightly less widely used" is doing a lot of heavy lifting there. For all of it except FFI.

I said clisp was slightly less widely used, not any of the other parts. Again, what exactly in their stack do you think is obscure?

These days, for new software, even OpenGL is obscure. And it stands out as odd--Vulkan is essentially the Khronos-approved successor to OpenGL, which is/was an API so thoroughly removed from the modern GPU model that any program using it would be CPU or system memory bound on modern hardware.